Elevations of serum lipids and lipoproteins have been established as a major risk factor for atherosclerosis, and many studies have proven that the diet profoundly affects these factors. Thus, attention has focused on the diet, not only as a likely major contributing factor to the variability in atherosclerosis incidence, but more importantly as a readily modifiable factor. Dietary manipulation is not only recommended as the first line of treatment in hyperlipidemia, but also as an important measure for the population at large. Nevertheless, many important aspects of the relationship between diet and lipid levels remain unclear. We propose to evaluate the effect of several of the currently recommended dietary regimens on lipoprotein metabolism. A more complete knowledge of this subject is important, especially in the following areas: 1) dietary effects on lipoprotein turnover; 2) dietary effects on lipoprotein-related enzymes; 3) heritability of plasma lipoproteins and response to dietary manipulations.